<!DOCTYPE html>
<title>Tests anchor positioned scrolling with fragmented containing block</title>
<link rel="help" href="https://drafts.csswg.org/css-anchor-position-1/#scroll">
<link rel="author" href="mailto:xiaochengh@chromium.org">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="support/test-common.js"></script>

<style>
body {
  margin: 0;
}
#multicol {
  column-count: 3;
  column-width: 90px;
  column-gap: 10px;
  width: 300px;
  height: 100px;
}

#cb {
  height: 300px;
  background: yellow;
  position: relative;
}

#spacer {
  height: 110px;
}

#scroller {
  overflow-y: scroll;
  height: 80px;
  background: blue;
}

#anchor {
  anchor-name: --a;
  width: 50px;
  height: 50px;
  background: orange;
  position: relative;
  top: 80px;
}

#target {
  position: absolute;
  left: anchor(left);
  bottom: anchor(top);
  position-anchor: --a;
  width: 50px;
  height: 50px;
  background: lime;
}
</style>

<div id=multicol>
  <div id=cb>
    <div id=spacer></div>
    <div id=scroller>
      <div id=anchor></div>
    </div>
    <div id=target></div>
  </div>
</div>

<script>
promise_test(async () => {
  scroller.scrollTop = 10;
  await waitUntilNextAnimationFrame();
  await waitUntilNextAnimationFrame();

  let targetRect = target.getBoundingClientRect();
  assert_equals(targetRect.top, 30);
}, 'Scrolling should work in fragmented containing block');
</script>
